1. Field of the Invention
The present invention relates to a packing device and a method for packing the stuffing-box of valves used for controlling the flow of process fluids in industry.
2. Description of the Prior Art
Referring to FIG. 4 a prior art valve is seen. When the valve is opened, process fluid can flow around the valve stem 19 and leak to the outside environment unless steps are taken to provide a positive seal around the valve stem. In accordance with standard practice, segmented rings 70, called packing rings, are stacked around the valve stem in the stuffing-box 16. They are then crushed down in the stuffing-box by a gland follower 72. Compressive force is applied to the gland follower by the yoke 74. The yoke 74 is retained in place by bolts 76,78. The bolts 76,78 matingly engage threaded holes 80,82 in bosses 84,86 on either side of the stuffing-box 16. The bonnet 28 supports the threaded portion of the stem 22. Turning the hand wheel 30 moves the stem 19, and the attached gate 20, up and down within the valve body 12.
The conventional method of preventing leakage around the valve stem suffers from a number of drawbacks. First, uneven torquing of the bolts 76,78, also known as gland fasteners, can cause the gland follower 72 and the stem 19 to bind, and/or the packing to leak due to the gland follower becoming tilted relative to the valve stem. Second, the old method of replacing the packing is time consuming and tedious, requiring the loosening of the gland fasteners, removing the yoke, removing the gland follower, removing the old packing using packing picks and pullers, and using a flashlight and mirror to check the stuffing-box for cleanliness. Reassembly of the valve is also time consuming because of the requirement that the gland fasteners be evenly tightened in order to prevent the binding and leakage mentioned previously.
To overcome the drawbacks enumerated above alternative methods and arrangements for valve packing have been proposed in the prior art.
U.S. Pat. No. 1,068,337, issued to Hahn, shows two tapering compression fittings which compress packing material to provide a seal around a moving shaft. Hahn does not show a bushing, having a tapered central passage, designed to be seated in the stuffing-box of a valve.
U.S. Pat. No. 1,704,152, issued to Stephens et al., shows a stuffing-box for sealing around a cable inserted into a pipe. Stephens et al. does not show a bushing having a tapered central passage.
U.S. Pat. No. 1,955,831, issued to Raybould, shows connectors for joining smooth pipe sections together. The connectors are secured to the pipe sections by compressing packing material between various compression fittings. Raybould does not show a bushing, having a tapered central passage, designed to be seated in the stuffing-box of a valve.
U.S. Pat. No. 2,385,156, issued to Newell, shows a pipe coupling for smooth pipe. The coupling includes two compression fittings which compress packing material between each other to secure the coupling to the pipe joint. Newell does not show a bushing having a tapered central passage.
U.S. Pat. No. 2,902,302, issued to Ackermann, shows a stuffing-box for sealing around the pump jack of an oil well. Ackermann does not show a bushing having a tapered central passage.
U.S. Pat. No. 3,468,566, issued to Nietzel, shows a compression fitting which compresses a ferrule to seal a pipe joint. Nietzel does not show a bushing having a tapered central passage.
British Patent Document Number 330,091, by Stephens, shows a packing gland for use in sealing around the spindles of the fuel valves of Diesel engines. The packing gland shown in British Document '091 includes a gland nut having a tapered central passage. However, British Document '091 does not show a bushing having a tapered central passage. Further, unlike the present invention, the bushing in British Document '091 is designed to fit into the central passage of the gland nut.
An article on page 224 of the April 1945 issue of Electronics magazine, shows a packing gland for use in sealing around propeller shafts and drive shafts of water pumps. The packing gland shown in Electronics magazine includes a cast case and a packing nut which threadably engages the cast case. A quantity of graphite impregnated cord is squeezed between the cast case and the packing nut to seal around the shaft. The surfaces of the cast case and the packing nut, which engage the graphite impregnated cord, are tapered. The packing gland shown in Electronics magazine does not include a bushing, having a tapered central passage, which can be seated in the stuffing-box of a valve. Further, the packing gland shown in Electronics magazine does not teach or suggest adhesively attaching the packing material to the tapered central passage of a threaded sleeve.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.